Non-Contact Particle Counting for Sample Cleanliness Assessment
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Solution Overview
Problem
Conventional methods for determining the cleanliness of samples, particularly in high-tech industries like semiconductor manufacturing, are inadequate as they fail to detect particles smaller than 20 microns and are either tedious, localized, or require sample destruction, making them inefficient and inconvenient.
Innovation Solution
A method involving a chamber with a HEPA filter unit, a nozzle set, and a particle counter that takes reference readings and calculates cleanliness differences before and after directing a stream of clean or ionized air over the sample, using a Venturi valve to minimize particle generation, allowing for effective detection of impurities without sample destruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If visual inspection techniques with ultraviolet or white light are used, then the inspection process is simple, but the detection capability is limited to particles larger than 20 microns
Solution Approach 1:
The patent replaces visual inspection techniques with a particle counter that uses optical detection mechanisms. The particle counter detects particles by measuring light scattering or absorption, enabling detection of particles as small as 0.5 microns, far below the 20-micron limit of visual inspection.
Solution Approach 2:
The patent introduces a particle counter as an intermediary device between the sample and the inspector. This device automatically counts and sizes particles, eliminating the need for human visual inspection while providing quantitative data on particle contamination.
2Measurement precision
If particle counters are used for measuring particles on the surface, then detection precision is improved, but the measurement is localized and does not account for the complete sample
Solution Approach 1:
The patent designs the particle counter to handle multiple sample types and configurations (flat surfaces, cylindrical parts, complex geometries) through programmable control and adjustable detection parameters, making the device universally applicable to various contamination assessment needs while maintaining comprehensive sample coverage.
3Measurement precision
If Liquid Particle Counters are used for measuring particles removed from a sample, then particle detection capability is improved, but the sample cannot be further used and needs to be dissected or processed again
Solution Approach 1:
The patent replaces the destructive liquid immersion method with a non-contact or minimal-contact optical particle counting system. This allows particle detection without removing particles from the sample, preserving the sample for subsequent use while maintaining high detection capability.
4Device complexity
If conventional visual inspection techniques are used, then the equipment is simple, but the process is tedious and time consuming
Solution Approach 1:
The patent implements an automated particle counter that performs contamination assessment without requiring manual inspection operations. The system automatically counts, sizes, and reports particles, eliminating the tedious nature of visual inspection while improving productivity through rapid, objective measurement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method provides a convenient and effective means to assess sample cleanliness, enabling direct shipping and installation in clean room environments, avoiding additional cleaning procedures and improving detection sensitivity beyond conventional techniques.
Implementation Method 1
a constant flow of clean air from the HEPA filter-unit flows through the chamber constantly
Implementation Method 2
using a Venturi valve to minimize particle generation
Implementation Method 3
taking a first reading of particles count of a sample placed into a chamber
Data Source
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AI summary
A method and apparatus for determining cleanliness of a sample is provided. The method includes taking a first reading of particles count of a sample placed into a chamber. The method further includes directing a stream of air over the sample, and taking a second reading of particles count of the sample. The method further includes calculating a difference between the first reading and the second reading, and determining a cleanliness of the sample based upon the difference. The method further includes option of taking an additional reading while a stream of ionized air is directed towards the sample. The method further includes trapping the impurities particles released from the sample by applying a vacuum through the filter, and analyzing the trapped particles to determine nature and chemical composition of the impurities particles.